Ignition System

ABSTRACT

An ignition system for a smoking machine is disclosed. The ignition system comprises an ignition head ( 12 ) for igniting one end of a smoking article which is held by a smoking machine, a sensor ( 18, 20 ) for detecting a distance between the end of the smoking article and the ignition head ( 12 ) in a direction parallel to the axis of the smoking article, and control means ( 21 ) for automatically adjusting ignition conditions in dependence on the detected distance. The sensor ( 18, 20 ) is arranged to detect the distance across a range of offset positions of the end of the smoking article in a plane perpendicular to the axis of the smoking article, which range is greater than the width of the end of the smoking article.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a National Stage filing of International ApplicationPCT/GB2005/004427, filed Nov. 16, 2005, entitled “IGNITION SYSTEM”,claiming priority to United Kingdom Application No. 0426162.4, filedNov. 29, 2004, entitled “IGNITION SYSTEM”. The subject applicationclaims priority to PCT/GB2005/004427 and to United Kingdom ApplicationNo. 0426162.4 and both references are expressly incorporated byreference herein, in their entirety.

BACKGROUND OF THE INVENTION

The present invention relates in general to improvements in and relatingto smoking machines for smoking articles such as cigarettes, cigars andcigarillos. More particularly, the invention relates to an improvedignition system for igniting smoking articles for smoking by a smokingmachine.

Regular testing of cigarettes on a smoking machine is an important partof any cigarette manufacturing process. A smoking machine serves tocreate a repeatable standardised environment for the analytical smokingof cigarettes. International and national standards, including ISOstandard 3308 (2000), have been put in place for standardising theoperation of smoking machines.

A smoking machine typically comprises at least one holder for acigarette, and a puffing means for drawing air in controlled fashionthrough the cigarette in regular short puffs in order to smoke thecigarette. The smoking machine may comprise or be adapted to engage withat least one lighter tool which comprises a heat source such as aresistive coil for lighting the cigarette. The machine usually alsocomprises or is adapted to engage with a variety of other tools,including tools for measuring or observing particular smokingcharacteristics, such as puff profile and leak check tools and/or airvelocity tools. The tools may be removable for use on a number ofdifferent machines.

It is desirable that the lighter tool should be capable of lighting thecigarette at the first attempt. Multiple attempts at lighting thecigarette may result in pre-charring, which may alter the smokingcharacteristics of the cigarette or otherwise disrupt any measurementswhich are to be taken. ISO standard 3308 (2000) indeed requires that asmoking machine should be capable of lighting cigarettes at the firstattempt and without pre-charring. Furthermore, the need for multipleattempts at lighting is clearly inefficient.

The distance separating the heat source of the lighter tool from thecigarette end has a profound effect on the success of ignition. If theheat source is too remote from the cigarette end, then the chances ofsuccessful lighting at first attempt will be diminished. On the otherhand, if the heat source is too close to the cigarette, then theignition process may result in heat damage to the cigarette which mayalter its smoking characteristics. Actual contact between the heatsource and the cigarette during ignition is particularly undesirable andis not permitted under ISO standard 3308 (2000). Typically, a separationof 0.25-0.75 mm between the heat source and the cigarette end at thepoint of ignition is viewed as desirable.

Some difficulty has however been encountered in achieving precisionpositioning (to within about 1.0 mm) of the cigarette and lighter tool.Once a cigarette has been loaded into a smoking machine, the position ofthe unlit tip with respect to the smoking machine depends primarily uponthe length of the cigarette and the depth of insertion of the cigaretteinto the smoking machine. Owing to the tolerances of manufacturingprocesses, the lengths of individual cigarettes from a batch typicallyvary within a range of 1-2 mm, giving rise to a correspondinguncertainty in the predicted length of a cigarette from the batch.Meanwhile, the depth of insertion of a given cigarette into a givensmoking machine may also vary by around 1-2 mm, depending primarily onthe force with which the cigarette is inserted into the machine. Thecombined effect of these uncertainties is an overall uncertainty of upto 4 mm in the predicted location of any single cigarette tip withrespect to the smoking machine. Precision positioning of the lightertool with respect to each cigarette tip, based on the predicted locationof the cigarette tip, is therefore impossible.

Co-pending United Kingdom patent application number 0306190.0 in thename of Molins plc, the entire subject matter of which is incorporatedherein by reference, discloses a lighter tool with a sensor in order todetect the distance between the lighter tool and the cigarette, and withcontrol means for adjusting the distance between the two so as to enablesuccessful ignition of the cigarette. In particular, it is proposed toprovide the lighter tool with a light beam, and to adjust the distancebetween the lighter tool and the cigarette until the light beam isbroken. In this way it can be ensured that the lighter tool and thecigarette are separated by a predetermined distance, so that effectivelighting of the cigarette can take place.

The above arrangement has been found to be effective in dealing withvariations in the position of the tip of the cigarette along the axis ofthe cigarette. However, this arrangement has been found to be lesseffective in dealing with misalignment of the cigarette in directionsperpendicular to the axis of the cigarette. Various causes ofmisalignment have been discovered, such as mis-insertion of thecigarette into the holder, droop of the cigarette, or accidentalknocking of the cigarette. It has been discovered that, if the cigaretteis misaligned, then it may not break the light beam, and as aconsequence it may not be possible to set the correct distance betweenthe lighter tool and the cigarette.

According to a first aspect of the present invention there is providedan ignition system for a smoking machine, the ignition systemcomprising:

-   -   an ignition head for igniting one end of a smoking article which        is held by a smoking machine;    -   a sensor for detecting a distance between the end of the smoking        article and the ignition head in a direction parallel to the        axis of the smoking article; and    -   control means for automatically adjusting ignition conditions in        dependence on the detected distance;    -   wherein the sensor is arranged to detect said distance across a        range of offset positions of the end of the smoking article in a        plane perpendicular to the axis of the smoking article, which        range is greater than the width of the end of the smoking        article.

By arranging the sensor to detect the distance across a range of offsetpositions of the end of the smoking article in a plane perpendicular tothe axis of the smoking article, the end of the smoking article can bedetected with much greater reliability than would otherwise be the case.Thus, even if the smoking article is misaligned, it may still bepossible to detect the position of the end of the smoking article andthus to light the smoking article reliably.

By axis of the smoking article it is preferably meant a line through themiddle of the smoking article along its length. Where the smokingarticle is a rolled article, such as a cigarette, the axis willgenerally be the axis on which it has been rolled.

The control means may be arranged to adjust the distance between theignition head and the smoking article and/or the operation of theignition head in dependence on the detected distance. For example, oncethe position of the end of the smoking article has been detected, thecontrol means may move the ignition head in a direction parallel to theaxis of the smoking article, so as to bring the ignition head into aposition suitable for ignition of the smoking article. Alternatively orin addition the control means may control an amount of heat emitted bythe ignition head, or the operation of the ignition head in relation tothe puff cycle of the smoking machine. Preferably the control meansadjusts ignition conditions so as to enable successful ignition of thesmoking article by the ignition head. Successful ignition may denoteignition at the first (or possibly a subsequent) attempt. Furthermore,successful ignition may denote ignition of the smoking article withoutany undesired heat damage to the article and/or without contact betweenthe smoking article and the ignition head.

The ignition system may be arranged to carry out a three stage processfor igniting the smoking article. In the first stage the ignition systemis brought into approximate alignment with the smoking article; in thesecond stage the distance between the end of the smoking article and theignition head is detected; and in the third stage the ignitionconditions are adjusted in dependence on the detected distance. Thus theignition system may be arranged to be brought into approximate alignmentwith the smoking article before the distance between the end of thesmoking article and the ignition head is detected. Alternatively theignition system may be arranged to carry out a two stage or a singlestage ignition process where either the tool moves directly to apredetermined position relative to the cigarette without the approximatealignment, or else moves to and at the same time lights the detectedsmoking article. These processes may be more efficient in terms of timetaken to light the smoking article.

The sensor may comprise an emitter and a detector. Preferably theemitter emits a beam of radiation which is detected by the detector.This can allow the sensor to detect the end of the smoking article bydetermining whether or not the end of the smoking article interrupts thebeam. The ignition system may then be arranged to carry out a “hunting”procedure to detect the end of the smoking article. For example, oncethe ignition head is in approximate alignment with the smoking article,if it is determined that the smoking article does not interrupt thebeam, then the ignition system may be moved closer to the smokingarticle until the beam is interrupted or partially interrupted. If it isdetermined that the smoking article does interrupt the beam, then theignition system may be moved away from the smoking article until thebeam is no longer interrupted or is partially interrupted. In eithercase, once a change in the state of the light beam is detected, theremay be a small movement of the ignition system in the opposite directionin order to correct for any overshoot. Thus in this arrangement the stepof detecting the distance in effect consists of detecting whether theignition head is too close to the smoking article, too far from thesmoking article, or at the correct distance.

The emitter may be arranged to emit radiation which covers an area in aplane perpendicular to the axis of the smoking article which hasdimensions greater than the depth of the electromagnetic radiation in adirection parallel to the axis of the smoking article. In this way, thesensor may be able to detect the end of the smoking article across arange of offset positions in a plane perpendicular to the axis of thesmoking article without compromising resolution of the sensor in thedirection parallel to the axis of the smoking article.

In one embodiment of the invention, the sensor comprises a plurality ofemitters which are arranged to emit radiation in a plane perpendicularto the axis of the smoking article. For example, the sensor may comprise2, 3, 4, 5 or some other number of emitters. This can allow the sensorto cover a greater area than if a single emitter were used.

The emitters may be arranged in a row such that each emitter emits abeam which runs substantially parallel to the other light beams.Alternatively the emitters may be arranged such that the beams crosseach other. For example the emitters may be arranged around part or allof a circle. In either case the beams may be separate or may overlap.

The or each emitter may be arranged so as to emit a beam which is widerin the direction perpendicular to the axis of the smoking article thanit is in the direction parallel to the axis of the smoking article. Forexample, a slit, a lens, a grating or some other means may be providedin order to make the beam wider in one direction than the other. Where asingle emitter is provided, this can enable the sensor to cover an areain the plane perpendicular to the axis which is sufficient to enabledetection of the end of the smoking article, without compromisingsensitivity in the direction parallel to the axis. This situation may beimproved even further by providing a plurality of emitters.

As an alternative or in addition, the or each emitter may be arranged toscan a beam in a plane perpendicular to the axis of the smoking article.For example, the emitter itself may be moved so as to scan the beam, ora variable beam deflecting means, such as a liquid crystal grating, maybe provided in order to scan the beam. In this case, a plurality ofdetectors may be provided, or a single detector may be provided whichcan also move or which has a detection area which is sufficient todetect the scanned beam.

As another alternative, or in addition, the system may further comprisemeans for moving the ignition system so as to move a beam from theemitter in a plane perpendicular to the axis of the smoking article. Inthis way the beam is arranged to scan by movement of the ignition systemitself.

The or each emitter may be an emitter of electromagnetic radiation. Theradiation may be in any part of the electromagnetic spectrum, such asvisible, infrared or ultraviolet light. The emitter may be, for example,an LED (light emitting diode), a laser, a bulb, or any other emitter ofelectromagnetic or other radiation.

The sensor may comprise a plurality of detectors. For example, thesensor may comprise a plurality of emitters and a plurality ofdetectors, and each emitter may be arranged to transmit a beam to acorresponding detector. All of the emitters may be arranged to emitbeams at the same time, or the emitters emit beams one or more at a timein a predetermined sequence. In the later case, this can allow theinterruption of a beam by the smoking article to be detected withgreater certainty, in particular where the beams from two or moreemitters overlap.

All of the emitters may emit radiation of substantially the same type.Alternatively each emitter may be arranged to emit different type ofradiation, and each detector may be arranged to detect radiation fromthe corresponding emitter, but not from other emitters. For example,each emitter could emit radiation of a different wavelength or differentpolarisation. This may be achieved, for example, by providing differenttypes of emitters, or by adjusting the operation of the emitters, or byproviding the emitters with suitable filters or polarisers. Thedetectors in turn may be arranged only to detect certain types ofradiation, or may be provided with suitable filters. This arrangementcan prevent a beam from one emitter interfering with that from another,which in turn may allow the interruption of a beam by the end of thesmoking article to be detected with greater certainty.

Preferably the emitters are spaced apart by no more than the width of asmoking article which it is desired to ignite. For example, the emittersmay be spaced apart by no more than the width of a cigarette. This canensure that at least one beam will be broken by the smoking article.However, it may be preferred to arrange the emitters closer together, sothat more than one beam will be broken by the smoking article. This canallow the end of the smoking article to be detected with greatercertainty, and can compensate for a failed emitter.

The ignition system may further comprise means for focusing radiationemitted from the or each emitter. For example, each emitter may beprovided with a lens in order to focus the radiation into a beam whichdoes not overlap with other beams, or which overlaps to a limitedextent. This can allow interruption of a beam by the end of the smokingarticle to be detected with greater certainty.

Since the ignition system operates in a smoky environment, it ispossible for smoke particles to accumulate on the emitters or detectors,which may reduce the amount of radiation emitted and/or detected.Furthermore, the amount of radiation which is emitted may reduce withageing of the emitter, and likewise the sensitivity of the detectors maydeteriorate over time. Thus the ignition system may be arranged to carryout a test procedure to determine the amount of radiation emitted by theor each emitter and/or detected by the or each detector. For example,where there is a plurality of emitters, each of the emitters may be litindividually in turn, and the amount of radiation received by thecorresponding detector may be measured. An amount of radiation emittedby the or each emitter may then be adjusted in dependence on the testprocedure. For example, the power supplied to the or each emitter maythen be adjusted, or the gain or range or polarisation of the emittersmay be adjusted, to ensure that all emitters emit radiation with thedesired power. For example all emitters may emit radiation withsubstantially the same power, or some may emit more radiation thanothers. Alternatively or in addition the sensitivity of the or eachdetector may be adjusted in dependence on the test procedure. Forexample, the gain of the detector may be adjusted though adjustment ofelectrical gain, or optical filtering or focusing at the detector may beadjusted.

The ignition head may comprise a heat source, which may emit heat forigniting the end of said smoking article by conduction, by convection orby radiation, or by any combination of conduction, convection andradiation. More typically, the heat source may emit heat by radiation orconvection or by a combination of radiation and convection. The heatsource may, for example, comprise a heatable coil, such as a resistivecoil. Such a coil will emit heat for igniting the end of said smokingarticle by a combination of electromagnetic radiation and convection ofheated air. The power of the coil may be in the region of 30-100 W, suchas between 40-60 W, or about 50 W. Alternatively, the heat source maycomprise a laser, or a halogen bulb, such as a halogen bulb of about120-200 W, which will emit heat for igniting the end of said smokingarticle primarily by electromagnetic radiation. Heat sources of all ofthese types are known in the art. Said heat source may conveniently bepowered by electricity.

In one embodiment of the invention the ignition head is arranged suchthat it can ignite the smoking article across a range of offsetpositions of the end of the smoking article. For example, the ignitionhead may be of sufficient dimensions, or may emit heat in a sufficientlylarge area, to ensure that the smoking article is lit even if thesmoking article is offset from its anticipated position in a directionperpendicular to the axis of the smoking article. This arrangement hasthe virtue of simplicity, but may result in unwanted heat being produceddue to the need for a relatively large heating area.

In another embodiment, adjusting means are provided for adjusting therelative position of the ignition head and the smoking article in adirection perpendicular to the axis of the smoking article, independence on an output of the sensor. For example, the sensor maydetect that the smoking article is offset by a certain amount, and theadjusting means may be arranged to adjust the relative position of theignition head and the smoking article so as to ensure that the ignitionhead will ignite the smoking article. This arrangement may provide theadvantage that a relatively small ignition head can be provided, whichreduces the amount of unwanted heat which is emitted.

The heat source may be capable of movement with respect to said smokingarticle, and said control means may be adapted for controlling movementof said heat source, whereby the heat source under the control of saidcontrol means can be moved into or halted at a selected position.Alternatively, or in addition, said control means may be adapted forcontrolling movement of a smoking article held by a smoking machine,whereby said smoking article under the control of said control means canbe moved into or halted at a selected position. By thus controllingrelative movement of said heat source and/or said smoking article inview of the known position of said end of the smoking article, apredetermined distance separating said heat source from said end of thesmoking article may readily be achieved.

Said sensor may be arranged such as to detect the end of a smokingarticle when said end is disposed at said predetermined distance fromthe heat source, or when said end is positioned such that aftersubsequent movement of said smoking article and/or said heat sourcealong a pre-set locus, said end will be disposed at said predetermineddistance from the heat source. Alternatively, said ignition system maybe arranged such that following detection of said end of the smokingarticle by said sensor, said heat source and/or said smoking article aremoved under the control of the control means such as to achieve saidpredetermined distance between said heat source and said end of thesmoking article.

Suitably, said control means may be adapted to ensure that said heatsource and said smoking article remain out of contact with one anotherduring emission of heat by the heat source.

Additionally or alternatively, said control means may be adapted toautomatically adjust the operation of said heat source followingdetection of the end of a smoking article by the sensor, such as toenable successful ignition of said end of the smoking article by theheat source. Parameters of the operation of the heat source which mayaffect the reliability and success of ignition include the temperatureof the heat source; the channelling of heat from the heat source to theend of the smoking article; the level and wavelength range ofelectromagnetic radiation that is applied by the heat source to the endof the smoking article; the length of time for which heat is applied tothe end of the smoking article for igniting the article; and the timingof the application of heat to the end of the smoking article forigniting the article with respect to the “puff cycle” of a smokingmachine. By adjusting any or all of these parameters, the control meansmay serve to enable successful ignition of a smoking article by the heatsource without any or any further adjustments in relative movement ofthe heat source and/or said smoking article. Said control means maytherefore be adapted for calculating the type and extent of anyadjustments to any of these parameters which may be required forenabling successful ignition, in view of the known position of the endof the smoking article (as detected by said sensor), and for securingthe performance of such adjustments. It will be appreciated however thatsaid control means may be adapted for adjusting any or all of theaforementioned parameters of the operation of the heat source inaddition to adjusting relative movement of said heat source and/or saidsmoking article.

In other embodiment of the invention, the sensor may be adapted toidentify the position of said end of the smoking article amongst a rangeof possible locations. In one possible aspect, therefore, said sensormay comprise a range-finding sensor, such as a laser or radar sensor,which is capable of transmitting signals which are adapted to bereflected from a target, detecting signals reflected from said target,and analysing said reflected signals, whereby the location of saidtarget can be calculated. Said range-finding sensor may be fixed in aknown position with respect to said heat source, and may be adapted foridentifying the location of said end with respect to said heat source.Alternatively, said range-finding sensor may be adapted to be fixed in aknown position with respect to said holding means, and may be adaptedfor measuring the location of said end of the smoking article withrespect to the holding means. In another possible aspect, said sensormay comprise any sensor as hereinabove defined which is capable ofdetecting the end of said smoking article when said end is in aspecified position, which sensor is adapted to be moved with respect tosaid heat source such as to hunt for said end, and means for identifyingthe position of the sensor with respect to said heat source, such thatthe location of said end, once detected by the sensor, can beidentified.

As yet a further alternative, said sensor may comprise a camera typedevice which is capable of visualising the smoking article and/or ashadow cast by the smoking article, whereby the position of the end ofthe smoking article may be detected.

In some embodiments, the arrangement may be such that said end of thesmoking article can be selectively shielded from said heat source, suchas to prevent substantial transfer of heat from said heat source to saidend. Thus, when the heat source and the smoking article are positionedfor ignition, said end may be shielded from the heat source and saidheat source may be energised without substantial transfer of heat fromthe heat source to the end during the course of energisation. Once theheat source is fully energised, said end may be exposed to the heatsource, thus enabling ignition of the end to take place.

Accordingly, said heat source may be adapted to move along a pre-setpath between a first exposed orientation, in which the heat source isarranged to face said end such that said end is exposed to the heatsource, and a second shielded orientation, in which the heat source isarranged to face away from said end such that said end is shielded fromsaid heat source. Alternatively, or in addition, one or more barriersformed from a heat-impermeable material may be provided for selectivelyshielding said end from said heat source. Said one or more barriers maybe adapted to be installed adjacent said heat source for shielding theheat source, and to be removed in order to expose said heat source.

Said control means may include control hardware which is programmed tocontrol the performance of the functions hereinabove defined. Inparticular, said control hardware may include processing means forreceiving said detection signal and for calculating the type and extentof adjustments which should be made to the components of the ignitionsystem and/or the smoking machine so as to enable successful ignition ofsaid smoking article, and for effecting said adjustments. Said controlhardware may be arranged to be located in a smoking machine, and/or insaid ignition system.

Said smoking article may be a rolled smoking article, such as acigarette, cigar or cigarillo. Suitably, said end of the smoking articlemay be the end which is ignited by a smoker in use; that is, thenon-filter end.

Preferably, said lighting system and said smoking machine may be capableof satisfying one or more ISO standards including ISO standard 3308(2000), and/or one or more FTC standards, and/or one or more CORESTAstandards, and/or any other applicable national or internationalstandards. Smoking machines suitable for use in conjunction with thepresent invention are widely available and in common use in the art.

Said smoking machine may be capable of holding a plurality of smokingarticles, and said lighting system may be adapted for igniting each ofsaid smoking articles consecutively. Preferably, said smoking machinemay be adapted for moving each smoking article which is to be ignited toa position such that the end of the smoking article is within a smalldistance, such as to within a few centimetres or a few millimetres, ofsaid ignition head, prior to detection of said end by the sensor andconsequent adjustment of the ignition head and/or the position of thesmoking article.

The invention also provides a smoking machine comprising an ignitionsystem in any of the forms described above.

According to another aspect of the invention there is provided a methodof automatically igniting a smoking article held in a smoking machineusing an ignition head, the method comprising:

-   -   detecting a distance between the end of the smoking article and        the ignition head in a direction parallel to the axis of the        smoking article;    -   adjusting ignition conditions in dependence on the detected        distance; and    -   igniting one end of the smoking article;    -   wherein said distance can be detected across a range of offset        positions of the end of the smoking article in a plane        perpendicular to the axis of the smoking article, which range is        greater than the width of the end of the smoking article.

Any of the apparatus features may also be provided as method features.

Preferred embodiments of the invention will now be described, purely byway of example, with reference to the accompanying drawings.

BRIEF SUMMARY OF THE INVENTION

An ignition system for a smoking machine is disclosed. The ignitionsystem comprises an ignition head (12) for igniting one end of a smokingarticle which is held by a smoking machine, a sensor (18, 20) fordetecting a distance between the end of the smoking article and theignition head (12) in a direction parallel to the axis of the smokingarticle, and control means (21) for automatically adjusting ignitionconditions in dependence on the detected distance. The sensor (18, 20)is arranged to detect the distance across a range of offset positions ofthe end of the smoking article in a plane perpendicular to the axis ofthe smoking article, which range is greater than the width of the end ofthe smoking article.

One object of the present disclosure is to describe an improved ignitionsystem for a smoking machine.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 shows parts of a smoking machine for use with embodiments of thepresent invention.

FIG. 2 shows a side view of parts of an ignition system in an embodimentof the invention.

FIG. 3 shows an end view of the ignition system.

FIG. 4 shows parts of an emitter unit.

FIG. 5 shows parts of a detector unit.

FIG. 6 shows parts of the ignition system during a hunting procedure.

FIG. 7 shows parts of the ignition system during ignition.

FIG. 8 shows a view of the ignition system during the hunting procedure.

FIG. 9 shows a view of the ignition system during ignition.

FIG. 10 shows an exploded view of the ignition system.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of theinvention, reference will now be made to the embodiments illustrated inthe drawings and specific language will be used to describe the same. Itwill nevertheless be understood that no limitation of the scope of theinvention is thereby intended, such alterations and furthermodifications in the illustrated device, and such further applicationsof the principles of the invention as illustrated therein beingcontemplated as would normally occur to one skilled in the art to whichthe invention relates.

Referring to FIG. 1, smoking machine 2 comprises a plurality ofcigarette holders 4 for holding cigarettes to be smoked. A suction unit(not shown) is provided for drawing air through the various cigarettesin order to smoke the cigarettes. The suction unit operates undercontrol of a control unit (not shown) in order to smoke the cigarettesin accordance with a particular puff cycle. Smoke from the cigarettes iscollected in smoke collection bags (not shown) for analysis.

The smoking machine 1 is provided with an ignition system 6 forautomatically lighting the various cigarettes. In this embodiment theignition system is mounted on a rail 8 and is driven by a stepper motorto bring the ignition system into approximate alignment with thecigarette it is desired to light.

Although FIG. 1 shows a linear smoking machine in which the cigarettesare mounted in a single row, the present invention can be used with anytype of smoking machine, including rotary smoking machines and machinesin which the cigarettes are mounted in two dimensional or threedimensional arrays. Some machines may have a lighter bar with severallighters on it, but no tool. Rotary machines have a lighting position,but may not have a separate tool, and the present invention can also beapplied to such smoking machines.

FIG. 2 shows a side view of parts of an ignition system 6 in anembodiment of the invention. Referring to FIG. 2 the ignition systemcomprises a cylindrical housing 10, an ignition head 12, a pair ofshutters 14, 16, an emitter unit 18, a detector unit 20 and a controlunit 21. The ignition head 12 in this embodiment is a resistive coilmounted in a protective holder which is formed from a heat-insulatingmaterial such as a ceramic material. The control unit 21 is arranged tocontrol the operation of the ignition head 12, the emitter unit 18 andthe detector unit 20. The control unit 21 may comprise one or moreprogrammed PCBs. As will be explained below, the emitter unit 18 isarranged to emit a plurality of light beams 22, and the detector unit 20is arranged to detect the plurality of light beams.

FIG. 3 shows an end view of the ignition system. As can be seen, in thisembodiment emitter unit 18 emits four light beams 22 ₁, 22 ₂, 22 ₃, 22₄, and detector unit 20 detects those four light beams.

The ignition system operates as follows. When it is desired to light acigarette, the ignition head is first switched on and allowed to reachthe correct operating temperature. At this stage the shutters 14, 16 areshut to prevent heat from preheating the cigarette. At this stage heatfrom the ignition head escapes upwards through a vent. The ignitionsystem 6 is then brought into a position in front of the cigarette. Thisposition will be approximately the correct position for ignition of thecigarette. However, due to variations in the length of the cigarette andthe depth of insertion of the cigarette, at this stage it is notpossible to achieve precise positioning of the lighter tool with respectto the cigarette.

The ignition system then begins a “hunting” procedure for the end of thecigarette. In this procedure, the ignition system determines whether ornot one or more of the light beams 22 is broken. If one or more of thelight beams is broken, the ignition system is too close to thecigarette. In this case the ignition system is moved away from thecigarette until the light beam is not broken, or is only partiallybroken. If however it is determined that none of the light beams arebroken, then the ignition system is moved closer to the cigarette untilone or more of the light beams is broken, or partially broken. Ifnecessary, overshoot may be corrected by arranging the ignition systemto move a small distance in the reverse direction once it has detectedthe breaking or restoration of the light beam.

Once the “hunting” procedure is completed, the ignition head 12 is apredetermined distance away from the end of the cigarette 24. Theignition head 12 is then brought forward towards the cigarette over adistance which will bring it into the correct position for lighting thecigarette. This distance is typically between 0.25 and 0.75 mm away fromthe end of the cigarette. At the same time the shutters 14, 16 arewithdrawn to allow the heat from the ignition head to light thecigarette. In this example the shutters are pivoted and movement of theignition head pivots the shutters into the open position.

In the first embodiment of the invention, a plurality of light beams 22are provided in order to detect the position of the end of thecigarette. This can allow the end of the cigarette to be detected withmuch greater reliability than if a single light beam were provided. Forexample, if the cigarette is misaligned, then it may not ever break asingle light beam, in which case it would be impossible to light thecigarette reliably. However, by providing a plurality of light beams,even if the cigarette is misaligned it may still be possible to detectthe position of the end of the cigarette and thus to light the cigarettereliably.

FIG. 4 shows parts of the emitter unit 18 in more detail. The emitterunit comprises four LEDs (light emitting diodes) 26 ₁ to 26 ₄, each ofwhich emits a respective light beam 28 ₁ to 28 ₄. The LEDs are spacedapart by no more than the width of the narrowest cigarette which it isdesired to detect. In practice it may be desirable to space the LEDscloser than this so that two or more beams will be interrupted by acigarette. This can provide more reliable detection, and may allowdetection of a cigarette even if one light beam fails, for example, dueto a faulty or dirty LED. The emitter unit is connected by means ofcable 30 to control unit 21.

FIG. 5 shows parts of the detector unit 20 in more detail. The detectorunit 20 comprises four light detectors 32, to 324 which are arranged todetect the light emitted by the LEDs in the emitter unit. The detectorunit 20 is connected by means of cable 34 to the control unit 21.

In one arrangement, each LED in the emitter unit 18 transmits a lightbeam to a single light detector in the detector unit 20. In this caseall of the LEDs are powered at the same time, and interruption of alight beam is detected simply by monitoring the outputs of each of thelight detectors. The LEDs may be provided with lenses to focus the lightor with masks in order to ensure that the light from one LED does notspill over to the light detector corresponding to another LED.

In another arrangement the LEDs are lit one at a time in a predeterminedsequence under control of the control unit 21. This can allow theinterruption of a light beam to be detected with greater certainty, inparticular where the light beams overlap.

Since the ignition system operates in a smoky environment, it ispossible for smoke particles to accumulate on the LED, which may reducethe amount of light emitted by the LED. Furthermore, the amount of lightwhich is emitted by the LED may reduce with ageing of the LED. In orderto ensure that sufficient light is emitted by the LEDs, the control unit21 carries out a test procedure when the ignition system is firstswitched on, and at other times if desired. In the test procedure, eachof the LEDs is lit individually in turn, and the amount of lightreceived by the corresponding light detector is measured. The powersupplied to the LED is then adjusted to ensure that all LEDs havesubstantially the same light output.

FIG. 6 shows parts of the ignition system during the hunting procedure.Referring to FIG. 6, the shutters 14, 16 can pivot about pivot points36, 38 respectively. During the hunting procedure the ignition head 12is withdrawn, and the shutters 14, 16 are biased into the closedposition by means of springs (not shown). In this way the ignition head12 is shielded from the cigarette.

FIG. 7 shows parts of the ignition system when the cigarette is beinglit. As can be seen from FIG. 7, the ignition head has been movedforward to a predetermined distance from the cigarette. The forwardmovement of the ignition head 12 causes the shutters 14, 16 to pivotabout pivot points 26, 38, and thus to open, thereby exposing theignition head to the cigarette. In this position the cigarette can belit by the ignition head.

FIG. 8 shows a view of the ignition system in the hunting position. Inthis position the ignition head is shielded by shutters 14, 16. Theemitter unit 18 emits light beams 22 ₁, 22 ₂, 22 ₃, 22 ₄ which aredetected by the detector unit 20. The position of the ignition system isadjusted in accordance with the hunting procedure described above untilthe ignition system is a predetermined distance from the cigarette. Atthis point the ignition head 12 is moved into the ignition position, asshown in FIGS. 7 and 9.

FIG. 10 shows an exploded view of the ignition system, withcorresponding parts given the same reference numerals.

While the invention has been illustrated and described in detail in thedrawings and foregoing description, the same is to be considered asillustrative and not restrictive in character, it being understood thatonly the preferred embodiment has been shown and described and that allchanges and modifications that come within the spirit of the inventionare desired to be protected.

1. An ignition system in a smoking machine, the ignition systemcomprising: an ignition head arranged to ignite one end of a smokingarticle which is held by a smoking machine; a sensor which detects adistance between the end of the smoking article and the ignition head ina direction parallel to the axis of the smoking article; a control unitwhich automatically adjusts ignition conditions in dependence on thedetected distance; and wherein the sensor is arranged to detect saiddistance across a range of offset positions of the end of the smokingarticle in a plane perpendicular to the axis of the smoking article,which range is greater than the width of the end of the smoking article.2. An ignition system according to claim 1, wherein the control unit isarranged to adjust the distance between the ignition head and thesmoking article in dependence on the detected distance.
 3. An ignitionsystem according to claim 1, wherein the control unit is arranged toadjust the operation of the ignition head in dependence on the detecteddistance.
 4. An ignition system according to claim 1, wherein the sensorcomprises an emitter and a detector.
 5. An ignition system according toclaim 4 wherein the emitter is arranged to emit radiation which coversan area in a plane perpendicular to the axis of the smoking articlewhich has dimensions greater than the depth of the radiation in adirection parallel to the axis of the smoking article.
 6. An ignitionsystem according to claim 1, wherein the sensor comprises a plurality ofemitters which are arranged to emit radiation in a plane perpendicularto the axis of the smoking article.
 7. An ignition system according toclaim 4, wherein the emitter is arranged so as to emit a beam which iswider in the direction perpendicular to the axis of the smoking articlethan it is in the direction parallel to the axis of the smoking article.8. An ignition system according to claim 4, wherein the emitter isarranged to scan a beam in a plane perpendicular to the axis of thesmoking article.
 9. An ignition system according to claim 4, furthercomprising a mechanism which moves the ignition system so as to move abeam from the emitter in a plane perpendicular to the axis of thesmoking article.
 10. An ignition system according to claim 4, whereinthe emitter is an emitter of electromagnetic radiation.
 11. An ignitionsystem according to claim 4, wherein the sensor comprises a plurality ofdetectors.
 12. An ignition system according to claim 1, wherein thesensor comprises a plurality of emitters and a plurality of detectors,and each emitter is arranged to transmit a beam to a correspondingdetector.
 13. An ignition system according to claim 12 wherein all ofthe emitters are arranged to emit a beam at the same time.
 14. Anignition system according to claim 12 wherein the emitters emit beams ina predetermined sequence.
 15. An ignition system according to claim 12,wherein each emitter is arranged to emit different type of radiation,and each detector is arranged to detect radiation from the correspondingemitter, but not from other emitters.
 16. An ignition system accordingto claim 12, wherein the emitters are spaced apart by no more than thewidth of a smoking article which it is desired to ignite.
 17. Anignition system according to claim 4, further comprising a lens whichfocuses radiation emitted from the emitter.
 18. An ignition systemaccording to claim 4, further comprising a mask which masks radiationemitted from the emitter.
 19. An ignition system according to claim 4,wherein the ignition system is arranged to carry out a test procedure todetermine the amount of radiation detected by the detector.
 20. Anignition system according to claim 19, wherein an amount of radiationemitted by the emitter is adjusted in dependence on the test procedure.21. An ignition system according to claim 19 wherein the sensitivity ofthe detector is adjusted in dependence on the test procedure.
 22. Anignition system according to claim 1 wherein the ignition head comprisesa heat source.
 23. An ignition system according to claim 1 wherein theignition head is arranged such that it can ignite the smoking articleacross a range of offset positions of the end of the smoking article.24. An ignition system according to claim 23 wherein the ignition headis of sufficient dimensions to ensure that the smoking article is liteven if the smoking article is offset from its anticipated position in adirection perpendicular to the axis of the smoking article by an amountgreater than the width of the smoking article.
 25. An ignition systemaccording to claim 24, further comprising a mechanism which adjusts therelative position of the ignition head and the smoking article in adirection perpendicular to the axis of the smoking article, independence on an output of the sensor.
 26. A smoking machine comprisingan ignition system, the ignition system comprising: an ignition headarranged to ignite one end of a smoking article which is held by asmoking machine; a sensor which detects a distance between the end ofthe smoking article and the ignition head in a direction parallel to theaxis of the smoking article; a control unit which automatically adjustsignition conditions in dependence on the detected distance; and whereinthe sensor is arranged to detect said distance across a range of offsetpositions of the end of the smoking article in a plane perpendicular tothe axis of the smoking article, which range is greater than the widthof the end of the smoking article.
 27. A method of automaticallyigniting a smoking article held in a smoking machine using an ignitionhead, the method comprising: detecting a distance between the end of thesmoking article and the ignition head in a direction parallel to theaxis of the smoking article; adjusting ignition conditions in dependenceon the detected distance; igniting one end of the smoking article; anddetecting said distance across a range of offset positions of the end ofthe smoking article in a plane perpendicular to the axis of the smokingarticle, which range is greater than the width of the end of the smokingarticle.